1. Field of the Invention
The present invention relates to a technique for removing a foreign substance that has attached itself to the surface of an optical element placed in front of an image sensor in an image capturing apparatus such as a digital camera.
2. Description of the Related Art
Many types of electronic image capturing apparatus (referred to simply as a “camera” below) typified by a digital still camera or video camera have become widespread rapidly owing to their immediacy and high affinity for personal computers. Such cameras obtain image data by opto-electronically converting the image of a subject using an image sensor and comprise generally small components such as the image sensor, a shooting optical system and an optical element such as a low-pass filter placed in front of the image sensor.
If a foreign substance such as dust attaches itself to, say, the optical element in the camera, the foreign substance itself appears in the image and causes a decline in the quality of the image. For this reason, various techniques for removing an adhering foreign substance by vibrating the optical element have been proposed and have started to be put into practice in recent years (see the specification of Japanese Patent Application Laid-Open No. 2003-333391).
In a case where an adhering foreign substance is removed by vibrating an optical element as described above, a vibrating device using a piezoelectric element generally is employed as the device that vibrates the optical element. For example, in a case where the vibrating device using a piezoelectric element malfunctions for some reason, there is the possibility that the vibration applied to the optical element will become too large and that this will destroy the optical element.
If the optical element is destroyed, it will be necessary to check the image by performing a shooting operation in order to detect such destruction. The problem which arises is that unnecessary labor is imposed upon the user.